Method and Apparatus for Delivering a Dose of a Gaseous Drug to a Patient

ABSTRACT

A method and device that can vary the dose of a gaseous drug provided to a patient based on a comparison of the normal resting breath rate for each individual patient and the current breath rate of the patient so that the patient does not become desaturated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.11/684,370, filed Mar. 9, 2007. Application Ser. No. 11/684,370 isincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a method of delivering doses of agaseous drug through an ambulatory device to treat a patient with lungdisease. The invention more particularly relates to an ambulatory devicethat provides a specific dose of a gaseous drug to a patient on eachbreath and can vary that dose to adjust to the patient's needs, as wellas deliver it at various flow rates to maximize comfort and decreasenoise.

2. Description of Related Art

The treatment of patients with lung disease often involves the use ofambulatory oxygen dosing systems.

Oxygen dosing systems are currently commonly referred to as conservingdevices because they only allow oxygen to be provided at fixed flowsduring a specific portion of the inhalation cycle. Conservers typicallyget oxygen from high pressure tanks that are delivered to the patient byan oxygen dealer. The design of these units is to conserve oxygen sothat oxygen is not provided when the patient cannot use it and thereforeit is not wasted. These types of devices were focused on using lessoxygen so that deliveries of the tanks to the patient were less frequentand thereby saving costs. However, while these conservers are ofteneffective at using less oxygen, they do not dose the patient properly.Clinical information on these types of devices can be found in, “A Guideto Understanding Oxygen Conserving Devices 2003” by Valley InspiredProducts which is herein incorporated by reference.

Research on oxygen conserving devices dosing can be found in thefollowing documents which are herein incorporated by reference: (a)Trina M. Limberg, Roberta S. Colvin, Maria Correa, Rosanna Costello,Cindy G. Morgan, and Andrew L. Reis, “Changes in Supplemental OxygenPrescription in Pulmonary Rehabilitation”; (b) A. Somfay, J. Porszasz,S. M. Lee, and R. Casaburi, “Dose-Response Effect of Oxygen onHyperinflation and Exercise Endurance in Nonhypoxaemic COPD Patients”,European Respiratory Journal, July 2001, volume 18 at 77-84; (c) LuisPuente-Maestu, Julia Garcia de Pedro, Yolanda Marinez-Abad, Jose MariaRuiz de Ona, Daniel Llorente, and Jose Manuel Cubillo, “Dyspnea,Ventilatory Pattern, and Changes in Dynamic Hyperinflation Related tothe Intensity of Constant Work Rate Exercise in COPD”, Chest, August2005, volume 128 at 651-656; (d) O. Diaz, C. Villafranca, H. Ghezzo, G.Borzone, A. Leiva, J. Milic-Emili, and C. Lisboa, “Breathing Pattern andGas Exchange at Peak Exercise in COPD Patients With and Without TidalFlow Limitation at Rest”, European Respiratory Journal, June 2001,volume 17 at 1120-1127; and (e) Peters, M M, Webb, K A, and O'donnell,De, “Combined Physiological Effects of Bronchodilators and Hyperoxia onExertional Dyspnea in Normoxic COPD”, Thorax, July 2006, volume 61 at559-567.

The fixed flow conserver devices can be categorized into either constantminute volume or constant volume conservers.

Constant volume devices really are fixed flow/variable time. On a devicethat has patient settings of 1-6, which can correspond to a patient'sLPM prescription, each setting would provide a fixed volume per breathdelivered. An example of this type of device can be seen in U.S. Pat.Nos. 5,005,570 and 5,370,112 to Perkins. These types of devices incommercial application typically have different settings to providedifferent volumes of oxygen. These devices typically provide for 16 ccof volume for each setting, so that a patient who is on a 2 settingwould receive 32 cc of oxygen at each inhalation cycle. The flow isfixed by an orifice against a known pressure and the device calculatesthe valve on-time to deliver a desired volume. This flow and valveon-time is the same for a patient who is breathing at 12 breaths perminute (“BPM”) as it is for a patient who is breathing at 35 BPM. Thedevice is designed to handle the highest expected breath rate andtherefore, delivers a higher than necessary flow in a shorter thannecessary window for patients breathing at a more relaxed rate.

Constant minute volume devices simply act as on/off valves at a fixedflow and do not predetermine a dose, but rather are demand valves. Theyturn on during inhalation, and turn off during exhalation. These devicessimply supply the patients' prescription flow. Since the I:E ratio isthought to remain constant, 1:2 for example, it is thought that thevalve will be on for a fixed percentage of the time in the course of aminute, and therefore are called constant minute devices. Constantminute volumes also often insert an accumulator chamber that isreplenished during valve off times. Assuming that the device fills thisaccumulator at a fixed rate (often 0.7-1 SLPM), then the patientdepletes this on every breath. The patient can never get more than thelimit of 1 SLPM of oxygen and if they breathe too fast, the accumulatorcan not be filled due to recovery time.

The above non-feedback devices do not adjust for a larger dose perbreath as the patient ambulates, and in many cases, the patients willdesaturate, i.e. have low oxygen levels in bloodstream.

Also, because the non-adjusting units give fixed doses at fixed flows,they do not adjust the flow down to minimize the flow required for thatbreath dose of oxygen. Fixed volume units give a specific, repeated doseby opening the valve for a fixed time, regardless of the inhalationtime. Because the flow is not minimized there is noise created throughthe nasal canula, creating an unpleasant experience for the oxygenpatient because the flow can startle the patient and cause nasaldryness.

The above prior art devices also are inefficient because oxygen iswasted. Oxygen from the above devices can be delivered during the secondhalf of inhalation. Oxygen delivered during the second half ofinhalation fills the upper airway where no gas exchange takes place andhas no therapeutic value. Additionally the above devices do not deliverdoses that fit the patient's need when their breath rate rises.

Further, some clinical personnel have migrated to using twoprescriptions for a patient; one for rest and another, higher settingfor the patient to use during ambulation. This points out the need foradditional oxygen during exercise, but also puts the burden on thepatient to remember to turn up their conserver when they get up andstart walking, and then to remember to turn it back down when they sitdown. Many of these patients are in their later years and can oftenforget to turn the device up or down, resulting in desaturation, oroxygen being wasted respectively.

Other than the above devices there are devices that use pulse oximetryas a feedback method and then adjusts to provide a target oxygensaturation. Examples of such devices can be found in U.S. Pat. No.6,532,958 to Buan et al.; U.S. Patent Application Publication No.20060225737 to Iobbi; U.S. Patent Application Publication No.20060213519 to Schmidt; U.S. Patent Application Publication No.20060011199 to Abdul-Aziz; U.S. Patent Application Publication No.20060005842 to Abdul-Aziz; U.S. Patent Application Publication No.20040159323 to Schmidt; and U.S. Patent Application Publication No.20030145852 to Schmidt.

However, oximetry is a very cumbersome means of feedback. A separateoximetry sensor must be attached to the patient usually on the patient'sfinger. Additionally, oximetry is not very accurate on a patient who isambulatory.

U.S. Pat. No. 6,880,556 tries to address the deficiencies with the priorart conservers. To do this U.S. Pat. No. 6,880,556 uses a predeterminednormal breath rate. This breath rate is used for all patients. A personof ordinary skill in the art would believe that there is a universalbreath rate that could be used, such as 20 bpm, that is the normalresting breath rate for all people and that this could be used toeffectively dose all patients. U.S. Pat. No. 6,880,556 uses an on/offvalve to deliver a volume of oxygen. All of the oxygen is delivered atthe same flow rate.

Historically, everybody skilled in the art and in the industry assumethat the normal resting breath rate is 20 breaths per minute. One ofordinary skill in the art would expect to be able to use 20 breaths perminute; and that at 20 breaths per minute, all patients would be keptsaturated.

However, through extensive research and clinical work we have figuredout that there is not a normal resting breath rate that applies to allpeople. We have discovered that normal resting breath rate is not thesame for every patient. There is a normal resting breath rate for eachand every patient that is particular to that patient and the normalresting breath rate for each individual patient varies over time. It caneven vary through the day. The normal resting breath rate for a personcan vary from hour to hour.

BRIEF SUMMARY OF INVENTION

The object of this invention is to overcome the deficiencies of theprior art.

Another object of this invention is to deliver oxygen to patients sothat all patients remain saturated at all times.

This invention provides for a method of giving a patient that has arespiratory disorder and has breathing function a dose of a gaseousdrug. A normal resting breath rate for the patient is determined. Thecurrent breath rate for the patient is monitored. The current breathrate is compared with the normal resting breath rate. Based on thecomparison a dose is provided to the patient. The dose can be deliveredduring the first two-thirds of an inhalation cycle. Normal restingbreath rate is determined by a control circuit. Changes in theinhalation to exhalation ratio can also be considered when providing thedose. This invention also provides for a method of giving a patient thathas a respiratory disorder and has breathing function a dose of agaseous drug using the ratio of inhalation to exhalation.

This invention also provides for a method of giving a patient that has arespiratory disorder and has breathing function a dose of a gaseous drugusing an inhalation window.

This invention also provides for an apparatus for giving a patient thathas a respiratory disorder and has breathing function a dose of agaseous drug. The apparatus has a control circuit connected to a vacuumpressure sensor that is connected to a patient to sense patientinhalation information. The control port has a connection port forconnection to a gaseous drug supply. The apparatus has a gaseous drugdelivery device that allows the volume and flow of the gaseous drug tobe varied. The gaseous drug delivery device could be a low flow valveand a high flow valve. Alternatively, the gaseous drug delivery devicecould be a variable flow valve.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of the apparatus for providing a dose of agaseous drug.

FIG. 2 is a block diagram of the apparatus for providing a dose of agaseous drug.

FIG. 3 is a graph of a patient data screen.

FIG. 4 is an Example of a Breath Rate Table.

FIG. 5 is a Breath Rate Chart.

FIG. 6 is a graph of a patient data screen.

FIG. 7 is a graph of patient data screen.

FIG. 8 is a graph of patient data screen.

FIG. 9 is a block diagram of the apparatus for providing a dose of agaseous drug with a variable flow valve.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Breath rate—the amount of breaths taken in a period of time. Typicallythis would be breaths per minute.

Normal resting breath rate—The usual amount of breaths for a patientunder normal resting conditions. Normal breath rate varies for eachperson and can vary from day to day and hour to hour. Normal restingbreath rate needs to be monitored and can be smoothed.

Determining a normal resting breath rate for the patient at a particulartime—Finding the normal resting breath rate for an individual patient ata certain time. This is a measured value calculated using an algorithmfor an individual patient. The normal resting breath rate for thepatient at a particular time can be a smoothed averaged baseline. It canbe determined by taking the Current Breath Rate (BR_(Cur)), and theCurrent Normal Breath Rate (BR_(CurNorm)), and weighting them bothproportionately, 20%, and 80% respectively or 10%, and 90% respectively,(or some similar ratio), to establish the New Normal Breath Rate(BR_(NewNorm)). This calculation is made on every breath except when thepatient is not at rest. When the device is first connected the firstcurrent Breath rate is 20. The rate is calculated continuously. However,if the current breath rate exceeds the current Normal Breath rate by avalue from +2 to +5 then the current breath rate is not used in thecalculation of the normal resting breathe rate because an increase ofsuch shows that the patient is not at rest. Preferably the value that isused is +3. So for example if the BR_(CurNorm) is 12 and the BR_(Cur) is16 this value is not used in the calculation of BR_(NewNorm). It is alsodesirable to allow a settling time after non-rest periods such that a 2minute delay is imposed after a patient's breath rate climbs. Using theprevious example, when the patient with a BR_(CurNorm) of 12 isambulating and their breath rate climbs to 16, they are viewed as “notat rest”. When they stop exercising, their breath rate declines, butthere is a settling time required for the patient to stabilize. As such,the unit excludes breaths when a patient exceeds BR_(CurNorm) by +3 andthen continues to exclude breaths for 2 minutes after they drop backbelow the +3 threshold.

Providing a dose—Supplying a volume of gas. This could be fixed volume,a predetermined defined pulse or fixed minute volume or any other methodof supplying a volume of gas. The volume could be varied based on thebreath rate.

Gaseous drug—a gas recognized in the official United StatesPharmacopeia. Examples are Oxygen, Nitrous Oxide, and Nitrogen.

Providing a dose of a gaseous drug—supplying a volume of a drug in gasform such as oxygen to a patient. The dose is less than the patient'stidal volume which is the amount of air breathed in or out during normalrespiration.

Chronic Obstructive Pulmonary Disease (“COPD”)—is a lung disease thatmakes it difficult for a person to breathe. The airways for a person tobe able to inhale and exhale are blocked. When COPD is severe, it canprohibit patients from doing basic tasks, such as walking a distance.COPD is also sometimes called Emphysema or chronic bronchitis. Oxygentherapy is used to treat COPD. Patients with COPD could be treated withthe method and apparatus described.

Respiratory disorder—an illness involving respiratory function that canbe treated. They would include COPD, interstitial pulmonary fibrosis andother illnesses that require oxygen therapy. It would not include asituation where oxygen is being used for life support.

Breathing function—A person is able to breathe on their own without lifesupport.

Monitoring the current breath rate—observing the breath rate at a pointand time.

Comparing the current breath rate with the normal resting breathrate—taking the current breath rate and evaluating it with respect tothe normal resting breath rate. For example the normal resting breathrate could be 15 and the current breath rate could be 30 indicating aneed for additional oxygen.

Providing a dose of the gaseous drug based on the comparison of thecurrent breath rate with the normal breath rate—delivering a dose basedon the difference between the current breath rate and the normal restingbreath rate. For example if the normal resting breath rate was 12 andthe current breath rate was 16 a dose of 32 cc might be deliveredinstead of 16 cc.

Typically the patient will have different settings that can be used witheach setting delivering an additional 16 cc per setting. When thecomparison shows a +3, +4 or +5 increase in breath rate and additional16 cc dose is given. This would be considered sport mode. A secondadditional 16 cc is given if the patient goes over a second threshold of+6, +7, or +8.

Dose is delivered during a first two-thirds of an inhalationcycle—providing a volume of gas to a patient within the first two-thirdsof time when the patient is breathing in.

Determining a standard ratio of inhalation time to exhalation timeduring a breath for a patient—A breath occurs when a patient breathes inand then exhales. It takes a person a certain amount of time to breathein and then exhale. “A ratio of inhalation time to exhalation timeduring a breath for a patient,” would be a comparison of the time ittakes a patient to breathe in versus the time it takes a person toexhale. An average ratio would be 1:2. 1 second inhale and 2 secondexhale would give a 3 second breath cycle and a breath rate of 20breaths per minute. This ratio could be a predetermined fixed value orit could be a value determined for an individual patient.

Monitoring the ratio of inhalation time to exhalation time—observing theratio of inhalation time to exhalation time for a patient.

Adjusting the dose of the gaseous drug provided based on a change in theratio of inhalation and exhalation—A volume of the gas has already beendetermined based on the breath rate however, that volume may be variedafter considering the change in the ratio of inhalation to exhalation.

Predetermining a fixed value—deciding in advance a set quantity to beused.

A control circuit—A programmable controller that could be a smallcomputer used for automation of processes, such as control of machinery.The control usually uses a microprocessor. The program is usuallycreated by a skilled technician. The program is stored in memory. Thereare special input/output arrangements. These connect the control to aprocess' sensors and actuators. The control circuit reads informationbeing monitored on the patient and then drives hydraulic cylinders ordiaphragms, magnetic relays or solenoids to control the dose beingdelivered.

Connected to—coupled with

Vacuum sensor—a device that determines changes in a gas stream. Thiscould also be a pressure sensor and is included in the definition ofvacuum sensor.

Senses a patient's inhalation—determining when a person inhales. Thesame canula tube is used to sense inhalation as is used to deliveroxygen, so that the sensor is ignored during the gas delivery time. Thesensor communicates that inhalation has begun, and the processordelivers the dose, at which time the vacuum sensor is ignored. When thedose is finished, the vacuum sensor is again monitored and the end ofinhalation and start of exhalation transition can be noted.

Breath rate monitored by the vacuum sensor and provided to the controlcircuit—the vacuum sensor looks at the breath rate and gives theinformation to the control circuit.

Normal resting breath rate is compared with current breath rate by thecontrol circuit—the control circuit determines whether the currentbreath rate is higher, lower, or the same as the normal resting breathrate.

Control circuit determines the dose of the gaseous drug to fit the needof the patient—based on the comparison of the current breath rate withthe normal resting breath rate, the control circuit selects an amount ofthe gaseous drug to be provided to the patient.

Control circuit adjusting a valve to deliver an appropriate dose andflow to the patient—the control circuit can have a valve closed oropened so that the patient receives the correct volume of gaseous drugand either controls the flow by choosing different valves or through aproportional valve.

Control circuit choosing from a low flow valve, a high flow valve, acombination of the low flow and high flow valve or a continuous flowswitch to deliver an appropriate dose to the patient—after determiningthe appropriate flow required so that the oxygen is delivered to patientwithin the first ⅔ of the inhalation window the control circuit canselect a valve or combination of valves.

Comparing the current ratio of inhalation time to exhalation time withthe standard ratio of inhalation time to exhalation time—taking thecurrent ratio of inhalation time to exhalation time and evaluating itwith respect to the standard ratio of inhalation time to exhalationtime.

Providing a dose of gas based on the comparison of the current ratio ofinhalation time to exhalation time with the standard ratio of inhalationtime to exhalation time—supplying a volume of a drug in gas form such asoxygen to a patient. The volume can be varied based on the comparison ofthe current inhalation time to exhalation time with the standard ratioof inhalation time to exhalation time.

Senses a patient's inhalation time and exhalation time—determining thetime it takes for a patient to inhale and the time it takes for apatient to exhale.

Current ratio of inhalation time to exhalation time is monitored by thevacuum sensor and provided to the control circuit—the vacuum sensortakes the current ratio of inhalation time to exhalation time and relaysthe information to the control circuit.

Determining an inhalation window—figuring out the time it takes forinhalation. This could be a predetermined amount of time or actuallyfigured out based on a particular patient. The current breath rate atthe last breath, is used to determine the delivery window for the nextbreath.

Determining an amount of the dose of the gaseous drug based on aduration of the inhalation window—basing a volume of the gaseous drug onthe time of the inhalation window.

Delivering the dose of the gaseous drug within a second inhalationwindow—providing a volume of the gaseous drug to the patient while thepatient is inhaling.

Dose is delivered during a first two-thirds of the second inhalationcycle—providing a volume of gas to a patient within the first two-thirdsof time when the patient is breathing in after the inhalation cycle isdetermined. For example if the inhalation cycle is a predetermined valuethen the second inhalation cycle would be the first inhalation by thepatient. If the inhalation cycle is first determined as the patienttakes the first breath with the apparatus connected then the secondinhalation would be the when the volume of gaseous drug is delivered.

Transmits the patient inhalation information to the controlcircuit—sending information regarding inhalation to the control circuit.

Connection port—place to link the gaseous drug with the apparatus.

Connection to a gaseous drug supply—Any type of gaseous drug storagecontainer or supply device.

Gaseous drug delivery device—a device that controls the volume and flowof the gaseous drug that is provided to the patent.

Allows the volume of the gaseous drug delivered to the patient to bevaried—the amount of the gaseous drug delivered can be changed.

Power supply—something that provides electricity. It could be batteries.

Low flow valve—a valve that permits between 3.5-4.0 liters per minute.An example of this type of valve is one made by Parker Hannifin'sPneutronics Division. Parker Hannnifin introduced a two-position,three-way, digital valve that is only 8 mm wide. The new modular device,called the X-valve, is made of glass reinforced PBT (polybutyleneterephthalate) and may be customized to meet a wide variety of medicaland analytical applications.

The modular design lets several valves mount side-by-side in a compactmanifold arrangement. The assembly is smaller than conventional systems,but the size does not compromise its operation. X-valves have a responsetime less than 10 msec and weigh about half that of valves in similarapplications. Moreover, the valve uses fewer parts, which means lesstolerance problems and fewer potential leak points with improvedreliability. This valve is used with an orifice that will allow the flowto be 3.5-4.0 liters per minute. Parker Pneutronics' X valves, or ParkerPneutronics' V2 Series valves, or Festo 10 mm MHP-1 solenoid valves canbe used.

Controlled by the control circuit—the control circuit operates.

High flow valve—valve that permits between 8.0-10 liters per minute. Anexample of this type of valve is the same Parker Hannnifin X-valve,however, a different orifice is used so that the flow is between 8.0-10liters per minute.

Continuous flow valve—is a valve that allows 2 liters per minute offlow. Can be any fixed liter flow based on the orifice or CV of thevalve/orifice combination, and the pressure at the input. In oneembodiment a 22-25 psig pressure regulation is used at the gas input.

Variable flow valve—a valve that can allow for different flow rates. Anexample of this type of valve is Festo proportional valve with MHP-1valve body.

Oxygen Conserver: a device that limits flow of oxygen to effectiveportions of the breath cycle. They vary from a simple demand valve thatis on during inhalation and off during exhalation, to a fixed dose pulseof oxygen delivered at the front end of the inhalation cycle.

Oxygen Saturation—oxygen saturation (SaO₂) measures the percentage ofhemoglobin binding sites in the bloodstream occupied by oxygen. At lowpartial pressures of oxygen, most hemoglobin is deoxygenated. At around90% (the value varies according to the clinical context) oxygensaturation increases according to an S curve and approaches 100% atpartial oxygen pressures of >10 kPa. A pulse oximeter relies on thelight absorption characteristics of saturated hemoglobin to give anindication of oxygen saturation.

Desaturation, or Hypoxemia—An SaO₂ (arterial oxygen saturation) valuebelow 90% is termed hypoxemia.

Sport mode—occurs when an extra dose of oxygen is provided because thepatient's breath rate increases. Typically, if the current breath rateis +3 then sport mode is entered and an extra dose is delivered.

DESCRIPTION

FIG. 1 shows a dosing apparatus 2 for providing a dose of gaseous drug.The dosing apparatus 2 is connected to a patient through a cannula tube6 and to a gaseous drug supply 8 through a connection port 10. Thedosing apparatus 2 has a vacuum pressure sensor 4, (it can be a vacuumor pressure sensor; and hereinafter will be referred to as a “vacuumsensor”) which monitors ongoing inhalation and exhalation. Theinformation obtained by the vacuum sensor 4 is sent to the controlcircuit 12 where it determines a normal resting breath rate, aninhalation window, a standard inhalation to exhalation ratio, thecurrent inhalation to exhalation ratio and current breath rate for thepatient.

Once all of the information is gathered the control circuit 12 then usesan algorithm to calculate and determine the amount of the dose, theestimated delivery time window for the next dose, and the minimum flowrate that can be used to deliver the dose within the delivery window,based on a comparison of the normal resting breath rate with the currentbreath rate. At that point the control circuit selects from a low flowvalve 14, a high flow valve 16, or a combination of both valves 14 & 16to deliver the appropriate dose to the patient. A gaseous drug deliverydevice in the embodiment is the combination of low flow valve 14 andhigh flow valve 16.

Typically the gaseous drug is oxygen. The dosing apparatus 2 may bepowered by a battery 20.

Typically the control circuit 12 would use the normal resting breathrate and compare it with the standard breath rate to calculate the doseof oxygen required for the patient. Alternatively the standardinhalation to exhalation ratio could be compared to the currentinhalation to exhalation ratio to calculate the dose of the oxygen. Anadditional alternative could be that an inhalation window is selectedand a dose calculated based on the duration of the window.

In an alternative embodiment of the invention, an inhalation window or astandard inhalation to exhalation ratio could be preprogrammed with setvalues for the standard inhalation window or a standard inhalation toexhalation ratio instead of the control circuit calculating this value.

As another alternative embodiment we could incorporate a single variableflow valve 17, as shown in FIG. 9, instead of multiple valves whichwould allow for a greater number of choices for flow and would fit thedose to the window more closely across the range of possibilities. Thesingle variable flow valve 19 is the gaseous drug delivery device.

A sample output graphic is shown in FIG. 3, and represents an example ofone patient who was tested. This was a test of a patient who was oncontinuous flow oxygen (no doser). The test had the patient rest for 5minutes, and then exercise on a treadmill for 10 minutes(approximately).

In the Breath Rate graphs in FIG. 3 there are two lines. One is thepatient's breath rate (starting below 20 breathes per minute) and theother line is the patient's normal resting breath rate (smooth linestaring at 25). The smooth line reflects a smoothed averaged baselinethat is derived by taking the Current Breath Rate (BR_(Cur)), and theCurrent Normal Breath Rate (BR_(CurNorm)), and weighting them bothproportionately, 20%, and 80% respectively, (or some similar ratio), toestablish the New Normal Breath Rate (BR_(NewNorm)). This calculation ismade on every breath.

Table 1 in FIG. 4 shows an exploded breath-by-breath example of a realpatient at start up. We use 20 BPM as the first BR_(Cur) value and thenrecalculate on each breath. The example is calculated using both an80/20 smoothing rate, and a 90/10 smoothing rate. This data set isgraphed out in FIG. 5. Chart 1 in FIG. 5 shows that the breath rate of apatient can jump around quite a bit, but the smoothed, first orderfilter breath rate gives a stable baseline that eliminates transients.

As can be seen, the smoothing filter is greater when only 10% weightingis used for the current breath than when a 20% weighting is applied. Wehave tried values of 5-25% weighting for the current breath rate. Themost preferable weighting factor which we are using currently is the20/80

This smoothing filter allows for patients to be tracked without reactingto short term changes. When a patient begins exercising, their smoothedbreath rate could climb as their breath rate goes up. When Sport Modedoses are delivered at +3 and +6 BPM over this baseline, the normalresting breath rate should not move over time with the patient'sexertion. In order to hold the normal resting breath rate to a breathrate that indicates rest, breaths from the smoothing calculation whilethe patient is in Sport Mode are excluded. This means that if apatient's normal resting breath rate is 15 BPM, that when they exceed 18BPM, an additional dose of oxygen is given, and the breaths are not usedin the smoothing filter. Additionally, there is a 2 minute delay afterthe patient's breath rate crosses back under the Sport Mode threshold(+3) setting before these breathes are used again in the filteringequation. This allows for use of only breaths that are not in SportModes (when patient is not at rest) for the calculation of normalresting breath rate and gives a recovery time for a patient who stoppedexerting themselves prior to using data for calculation of the normalresting breath rate.

In order to illustrate the differences between patients, and the need tocalculate the normal resting breath rate for each patient, please seeFIGS. 6-8.

FIG. 6 shows a patient on a standard conserver that only gives 16 cc persetting (32 cc for a 2 LPM patient). Notice that this patient's restingbreath rate is 16 BPM. The shaded area represents exercise. We could seehere that using a “Normal Breath Rate” of 20 would not be appropriatefor this patient. Notice the desaturation that accompanied exercise bythe dip in the top line in the Sa O₂, HR row.

FIG. 7 shows another patient whose normal breath rate is more along thelines of 24 BPM. Notice that this patient was on the dosing algorithm,so when they exceeded 3 BPM over their personal threshold, they weregiven additional oxygen in Sport Modes, 1 & 2. The additional doses aretracked on the bottom graph. We can also see here that the saturationremained stable at >95% Sa O₂. Note: The oximeter probe became dislodgedduring exercise which caused the gaps in reading, but in general couldtrend to positive results.

FIG. 8 shows yet another patient who underwent the same test protocoland it can clearly be seen that this patient does not have a similarbreath rate to the previous examples. The patient in FIG. 8 has a normalresting breath rate of less than 15 BPM. Had the industry norm of 20 BPMbeen selected as the normal resting breath rate, this patient would notbe given additional oxygen when they need it.

The more we monitored patients that were tested, the more it wasrealized that each patient is different and that re-testing them atlater points in time showed additional variances. Patients' conditionschange over time and their disease is better and worse on any given day.Because of this, there is not any fixed predetermined value for “normalbreath rate” that will work for all patients.

At this time, one embodiment uses two valves in the system, that incombination give a total flow capacity on the order of 13-16 LPM(currently using 14 SLPM flow combination). This flow is selectedprimarily because this is the maximum flow that most patients cantolerate. The optimum condition is to use the highest flow that the canbe used and that is accepted by the patient, because this allows fordelivery of the largest dose in the smallest delivery window.

This does not equate to an answer of more valves equals more flow. Otherunits already give flow in this range with a single valve, and theylikewise were selected to be the maximum that the patients can tolerate.The reason for multiple valves (flows) was to be able to NOT delivermaximum flow when it is not needed. If a patient is breathing at a slowrate, sitting, resting, such as in church, they likely do not want orneed flows of 16 SLPM to get their dose in the appropriate time.

The higher the flow, the greater the dose that can be delivered in agiven delivery window, but the practical limit is patient tolerance. Asan example, if 14 SLPM is chosen as the max flow, or an existing unitdelivers at 14 SLPM (all the time with one valve/orifice), the dose isequal to:

Dose=Valve on Time(V _(OT))*Max Flow(F _(max))/1000

Where: V_(OT) is in msec

-   -   F_(max) is in ml/sec

If the dose is predetermined and the maximum flow is set, then the onlyvariable is the valve on-time. If the dose is to be delivered within the“delivery window”, (60% of the inspiratory cycle), then the patient'sinhalation time can not exceed 167% of the valve on-time. This is thepractical limit of this device and of every device on the market.

The multiple flows are used to allow the device to stretch the tolerancefor short times when more flow is needed while still maintaining lower,acceptable flows when it is not needed. In addition to this, the devicegives very low flows when a patient is at rest. As an example, a patientthat is on a 2 setting would receive 32 ml dose. Let's assume that theyare at rest and breathing at 14 BPM (resting). On a standard doser thatdelivers at a fixed flow of 14 SLPM, the following would be true:

F _(Max)=14 SLPM*(1 Min/60 Sec)*(1000 ml/Liter)=233.33 ml/sec

V _(OT)=[(32 ml)/(233.33 ml/sec)]*1000=137.14 msec

This patient's delivery window, assuming an I:E ratio of 1:2, would be:

D _(Win)=(60 sec/1 min)*(1 min/14 Breaths)*(⅓ Inhale to totalbreath)*(0.60)=850 msec.

A fixed flow device operating in this condition, would deliver a dose in137 msec, when the dose could have been delivered at a much lower flow,up to 850 msec, which is more comfortable for the patient.

This device would have chosen a flow of 4 SLPM, and delivered this dosein:

F _(Selected)=4 SLPM*(1 Min/60 Sec)*(1000 ml/Liter)=66.67 ml/sec

V _(OT)=[(32 ml)/(66.67 ml/sec)]*1000=480 msec

Note that this is still well within the allowable delivery window, butis at a considerably lower flow and is therefore, very comfortable forthe patient, will cause less nasal dryness, and is quieter for thepatient. Note that patients are very concerned with the noise that theirequipment generates. They would like for their therapy to be asinconspicuous as possible, and lower flow produces lower noise.

In a second embodiment a single proportional valve will be used thatwill provide a range of flows and therefore allow the device to alwaysuse the delivery window to minimize flow. In this same case, thefollowing delivery logic would be used.

F _(Selected)=[(32 ml)/(0.850 sec)]=37.65 ml/sec flow

(37.65 ml/sec)*(60 sec/1 Min)*(1 Liter/1000 ml)=2.26 SLPM

The first embodiment will allow the device to choose three flows betweentwo valves, A and B, of:

Flow A=4 SLPM

Flow B=10 SLPM

Flow A+B=14 SLPM

With a proportional valve, the device chose the exact flow to allow usto fit the dose into the delivery window.

With reference to FIG. 2, a therapeutic oxygen gas 22 is supplied from aliquid oxygen Dewar 24. Due to natural heat losses of the container,there is a natural evaporation rate that keeps a gas layer in the Dewar24 which builds in pressure as more volume converts from liquid togaseous oxygen. This gas is maintained at a desired pressure of 25 psiby a pressure relief valve 26 embedded in an economizer valve system.The economizer valve system makes use of the gaseous oxygen for patienttherapy, and will supplement this with liquid oxygen if needed. Whenliquid oxygen is used, due to rapid consumption that outpaces theevaporation rate of the Dewar, it is delivered through a length oftubing to warm it to adequate levels prior to delivery to a patient.This system provides oxygen to the dosing system at a static and stablepressure of 25 psig. Note that the dosing system can be altered tovarious pressures or sources inasmuch as they are at stable pressure.

A patient interface 28 is comprised of a patient selector switch 30which allows the patient to select their prescribed oxygen flow ratewith settings of; 0, 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 standard litersper minute (SLPM) of oxygen. This selection reflects the continuous flowtherapy that the patient was prescribed, and is converted to a breathdose volume by the microprocessor. Base dosing equivalents shouldpreferably reflect 16 cc of oxygen for each SLPM setting such that aflow selection of 1.0 SLPM will result in a base or normal dose of 16cc, while a flow selection of 2.0 SLPM will result in a base, or normaldose of 32 cc, and so on.

The patient connects to the oxygen port with a cannula tubing, which isinternally connected to a pressure sensor 4. The pressure sensor couldbe a vacuum or pressure sensor 4. When the patient inhales, the pressuresensor 4 output changes. A microprocessor 32 monitors the pressuresensor 4 and converts the analog signal to a digital reading and usesthis signal change to indicate transitions between inhalation andexhalation. By monitoring these transitions and tracking with aninternal clock, the microprocessor 32 can determine the breath patternof the patient, specifically, beginning of inhalation, length ofinhalation, length of exhalation, length of breath, current breath rate,and the ratio of inhalation to exhalation (I:E ratio). It should benoted that the vacuum/pressure signal should be ignored as a breathindicator during oxygen delivery since the flow out to the patient iscarried in the same tube as the vacuum/pressure signal to the sensor.During oxygen delivery, the signal is discarded, or can be used to trackthat dose was delivered, and then monitored once again after the dose isfinished.

As a preferred embodiment, the microprocessor 32 monitors the currentbreath rate and maintains a filtered normal resting breath rate. It isknown that a patients' breath rate increases with exertion, and byexcluding higher breath rates from the filtering, a normal restingbreath rate can be developed by the microprocessor and is specific toeach patient and can change over time. On each breath, the algorithmcombines the normal resting breath rate to the current breath, andweights them at 80% and 20% respectively. This then becomes the newnormal resting breath rate. Whenever a patient's current breath ratecrosses a threshold of >3 breaths per minute (BPM) higher than theirnormal resting breath rate, it and all subsequent breaths are excludedfrom this equation, as well as all breaths for an additional 2 minutes.The result is a smoothed normal resting breath rate that reflects apatient's at-rest condition. As an alternative, the unit could alsomonitor and react to I:E ratio changes as an indicator of rest orexertion. By monitoring the current breath rate, the microprocessor alsocalculates a delivery window for the next breath that is ⅔ of theinhalation of the current breath.

The apparatus delivers the before mentioned base dose of 16 cc persetting of patient continuous flow setting while the patient is at rest.When the patient's breath rate exceeds 3 BPM over the normal restingbreath rate, which is re-calculated on each breath, the microprocessor32 controls the system to deliver a Sport Mode₁ dose that is equivalentto the base dose, plus an additional 16 cc. Additionally, another SportMode₂ dose, also 16 cc additional, is delivered if the patient exceeds 6BPM over their normal resting breath rate. In doing so, the apparatusgives a patient more oxygen when they ambulate. In general, the devicelooks at each breath to monitor if the patient is resting or ambulating,and if they are ambulating, it provides higher doses of oxygen to tracktheir level of exertion.

The apparatus has two solenoid valves 14 and 16 each combined with aflow restrictor 15 and 17 that when opened, allow flows of 4 or 8 SLPMrespectively. These two flows (4 & 8 SLPM), along with a 12 SLPM flowwhen both valves 14 and 16 are opened simultaneously, providing threedifferent flow options for the delivery of the oxygen. While otherdelivery devices use one flow and only vary the valve on-time to controlthe dose, this device selects the flow based on the expected deliverywindow of the next breath in relation to the volume to be delivered. Themicroprocessor 32 determines the next dose volume as explainedpreviously, and compares this to the delivery window, and then uses thelowest flow option to deliver this volume in the allotted time. Themicroprocessor 32 then opens one of the two valves 14 or 16, or both 14and 16 by digital signal to the valve drivers. By maintaining lower flowrates when possible, the patient does not receive excessive flows thatpush the dose into a very small delivery window that may be appropriateat high breath rates, but is not necessary at lower resting breathrates. By always delivering at the lowest flow option, the deviceprovides a quieter and more subtle oxygen dose delivery whenappropriate. This lower flow delivery also minimizes nasal dryness, acommon complaint of patients on higher flow dosing systems.

Also included on the patient interface is an LED indicator that isilluminated green during the dose delivery to notify and assure thepatient that doses are being delivered, and illuminates red during thedose delivery if the batteries are getting low and alerts them of theneed to replace or recharge the batteries.

There is a Continuous Flow/Pulse Delivery (CF/PD) switch on the patientinterface that allows a patient to bypass any and all dosing, and todraw oxygen from the source. This is typically considered a backup andis most often used in the event of a low battery condition. In the CFmode, the CF/PD switch routes oxygen through a Flow Restrictor (orifice)such that the continuous flow to the patient is 2 SLPM. This flowrestrictor can be changed for other flow rates so that the device can beset up specifically for each patient. This switch routes the flow path,but also engages an electric switch that disables the dosing circuit andprevents the doser from trying to provide pulses while the user hasselected continuous flow.

1. A method for providing a dose of a gaseous drug to a patient that hasa respiratory disorder comprising: a. determining a normal restingbreath rate for the patient at a particular time; b. monitoring thecurrent breath rate of the patient; c. comparing the current breath ratewith the normal resting breath rate; and d. providing a dose of thegaseous drug based on the comparison of the current breath rate with thenormal breath rate.
 2. The method as recited in claim 1 wherein the doseis delivered during a first two-thirds of an inhalation cycle.
 3. Themethod as recited in claim 1 including: a. determining a standard ratioof inhalation time to exhalation time during a breath for a patient; b.monitoring the current ratio of inhalation time to exhalation time; c.comparing the current ratio with the standard ratio; and d. adjustingthe dose of the gaseous drug provided based on a change in the ratio ofinhalation and exhalation.
 4. The method as recited in claim 1 includingvarying the flow of the dose delivered to the patient so that less flowwill be used when the patient is close to normal resting breath rate. 5.The method as recited in claim 1 wherein the normal resting breath ratefor the patient is determined by a control circuit that is connected toa vacuum sensor that senses a patient's inhalation.
 6. The method asrecited in claim 5 wherein the current breath rate is monitored by thevacuum sensor and provided to the control circuit.
 7. The method asrecited in claim 6 wherein the normal breath rate is compared withcurrent breath rate by the control circuit.
 8. The method as recited inclaim 7 wherein the comparison of the current breath rate with thenormal resting breath rate is done by the control circuit and based onthe comparison, the control circuit determines the dose of the gaseousdrug to fit the need of the patient.
 9. The method as recited in claim 8wherein the dose is provided by the control circuit adjusting a valve todeliver an appropriate dose to the patient.
 10. The method as recited inclaim 8 wherein the dose is provided by the control circuit choosingfrom a low flow valve, a high flow valve, a combination of the low flowand high flow valve to deliver an appropriate dose to the patient.
 11. Amethod for providing a dose of a gaseous drug to a patient that has arespiratory disorder comprising: a. determining a standard ratio ofinhalation time to exhalation time during a breath for a patient; b.monitoring the current ratio of inhalation time to exhalation time; c.comparing the current ratio of inhalation time to exhalation time withthe standard ratio of inhalation time to exhalation time; and d.providing the dose of the gaseous drug based on the comparison of thecurrent ratio of inhalation time to exhalation time with the standardratio of inhalation time to exhalation time.
 12. The method as recitedin claim 11 wherein the dose is delivered during a first two-thirds ofan inhalation cycle.
 13. The method as recited in claim 11 includingvarying the flow of the dose delivered to the patient so that less flowwill be used when the patient is close to the standard ratio ofinhalation time to exhalation time.
 14. The method as recited in claim11 wherein the standard ratio of inhalation time to exhalation time isdetermined by a control circuit that is connected to a vacuum sensorthat senses a patient's inhalation time and exhalation time.
 15. Themethod as recited in claim 14 wherein the standard ratio of inhalationtime to exhalation time is monitored by the vacuum sensor and providedto the control circuit.
 16. The method as recited in claim 15 whereinthe standard ratio of inhalation time to exhalation time during a breathfor a patient is compared with the current ratio of inhalation time toexhalation time by the control circuit.
 17. The method as recited inclaim 16 wherein the comparison of the current breath rate with thestandard ratio of inhalation time to exhalation time is done by thecontrol circuit and based on the comparison, the control circuitdetermines the dose of the gaseous drug to fit the need of the patient.18. The method as recited in claim 17 wherein the dose is provided bythe control circuit adjusting a valve to deliver an appropriate dose tothe patient.
 19. The method as recited in claim 17 wherein the does isprovided by the control circuit choosing from a low flow valve, a highflow valve, a combination of the low flow and high flow valves or acontinuous flow switch to deliver an appropriate dose to the patient.20. A method for providing a dose of a gaseous drug to a patient thathas a respiratory disorder comprising: a. determining an inhalationwindow; b. determining an amount of the dose of the gaseous drug basedon a duration of the inhalation window; and c. delivering the dose ofthe gaseous drug within a second inhalation window.
 21. The method asrecited in claim 20 wherein the dose is delivered during a firsttwo-thirds of the second inhalation cycle.
 22. The method as recited inclaim 20 wherein the inhalation window for the patient is determined bypredetermining a fixed value.
 23. The method as recited in claim 22wherein the inhalation window for the patient is determined by a controlcircuit that is connected to a vacuum sensor that senses a patient'sinhalation.
 24. The method as recited in claim 23 wherein the secondinhalation window is determined by the vacuum sensor and provided to thecontrol circuit.
 25. The method as recited in claim 24 whereindetermining the amount of the dose based on the duration of theinhalation window is determined by the control circuit.
 26. The methodas recited in claim 25 wherein the dose is provided by the controlcircuit adjusting a valve to deliver an appropriate dose to the patient.27. The method as recited in claim 26 wherein the dose is provided bythe control circuit choosing from a low flow valve, a high flow valve, acombination of the low flow and high flow valves or a continuous flowswitch.
 28. A dosing apparatus for providing a dose of a gaseous drug toa patient that has a respiratory disorder comprising: a. a controlcircuit; b. a vacuum pressure sensor that is connected to a patient tosense patient inhalation and transmits the patient inhalationinformation to the control circuit; c. a connection port for connectionto a gaseous drug supply; d. a gaseous drug delivery device that allowsthe volume of the gaseous drug delivered to the patient to be varied;and e. a power supply that provides power to the apparatus.
 29. Theapparatus as recited in claim 28 wherein the gaseous drug deliverydevice comprises: a. a low flow valve controlled by the control circuit;and b. a high flow valve controlled by the control circuit.
 30. Theapparatus as recited in claim 29 including a continuous flow valvecontrolled by the control circuit.
 31. The apparatus as recited 28wherein the gaseous drug delivery device comprises a variable flowvalve.
 32. The apparatus as recited in claim 28 wherein the gaseous drugsupply is a liquid oxygen reservoir.
 33. The method as recited in claim1 wherein the normal resting breath rate is smoothed value calculated byan algorithm.
 34. The method as recited in claim 33 wherein in thealgorithm is the following:${{Normal}\mspace{14mu} {resting}\mspace{14mu} {breath}\mspace{14mu} {rate}} = \frac{{{BR}_{Cur}(x)} + {{BR}_{curnorm}(y)}}{100}$Where x=1-99 and y=100−x.
 35. The method as recited in claim 4 wherein xis 0-25.
 36. The method as recited in claim 35 wherein Normal restingbreath rate is calculate on every breath except if BR_(Cu)+2 or moregreater than BR_(curnorm) then the Normal resting breath rate remainsthe same and the calculation of does not start again until the BR_(Cu)is within 2 of BR_(curnorm).
 37. The method as recited in claim 35wherein the calculation does not start again until 2 minutes after theBR_(Cu) is within 2 of BR_(curnorm).
 38. The method as recited in claim35 wherein Normal resting breath rate is calculate on every breathexcept if BR_(Cu)+3 or more greater than BR_(curnorm) then the Normalresting breath rate remains the same and the calculation of does notstart again until the BR_(Cu) is within 3 of BR_(curnorm).
 39. Themethod as recited in claim 35 wherein the calculation of does not startagain until 2 minutes after the BR_(Cu) is within 3 of BR_(curnorm).